1. Field of the Invention
The present invention relates to fetal monitoring and, more particularly, to an electronic external fetal monitoring system that includes a self adhering single use dermal patch including embedded sensors that can be attached to the skin of an expectant maternal patient and is configured to record fetal heart rate, uterine activity, and uterine integrity.
2. Description of the Related Art
Accurately evaluating the well-being of a fetus during labor and delivery is tantamount in providing a plan of care that will ensure the most desired outcome (i.e., healthy newborn and mother). Electronic Fetal Monitoring technology/devices, EFM, was developed in the 1960's, and became routinely used in hospitals by the late 1970's. EFM is used to evaluate fetal well-being during the labor process by recording fetal heartbeat and frequency of uterine contractions via two monitors—an ultrasound device (US) and tocodynameter (TOCO), respectively.
Today EFM is the most common obstetrical procedure in the US, estimated at 8 million applications annually. Virtually every woman undergoes EFM during pregnancy, and labor and delivery. EFM has also become the standard of care in obstetrical settings worldwide.
In brief, during labor, care providers perform a Leopold Maneuver on the gravid abdomen to try to detect the lie of the fetus in the uterus. Placing the US over the fetal back, once detected, is usually the best location to record consistent fetal heart beat. Ultrasonic gel must be applied between the US device and the skin surface to function properly. The US is held to the abdomen with an elastic belt. The TOCO is applied to the abdomen above the umbilicus where the fundal height of the uterus is palpated, and is held to the upper part of the abdomen by an elastic belt.
EFM technology has not changed much since its inception, although care providers are relying more heavily on the data this technology provides and some improvements have been made in the interpretation of this data. It is therefore very important to record the most consistent, accurate, and reliable data possible. Physicians are under tremendous pressure from lawsuits to intervene when any indication elicited from the EFM technology alerts the physician to a change in fetal well-being during labor. Whenever there is inconsistent data from the EFM technology, care providers often have to choose the plan of care with the least amount of risk to the fetus. In many cases this means cesarean birth.
Current interpretation of data gathered by conventional EFM technology involves subjective interpretation of the data by the clinician, i.e., the clinician uses his/her trained eye to monitor a strip of data indicating fetal heart rate and uterine contractions over a specific period of time (as should be understood by those skilled in the art).
The first thing a clinician determines when interpreting EFM data is the baseline fetal heart rate. The baseline is defined as the average heartbeat between contractions, consistent for 10 or more minutes; for example, 140 bpm (beats per minute). The next step is to determine variability. Variability is the variance in the baseline, also described in beats per minute, bpm. There are four categories of variability: Absent: none detected; minimal: 1-5 bpm; moderate: 6-25 bpm; and marked: >25 bpm. Moderate variability indicates fetal well-being, while absent, minimal, or marked variability can indicate fetal distress.
The next step is to determine the presence or not of accelerations in the fetal heart rate. For neonates, accelerations are defined as an increase in fetal heartbeat by 15 bpm over baseline for a duration of 15 seconds. As an example clinical assessment, the clinician may note fetal heartbeat 140 bpm, moderate variability, with accelerations noted.
Finally, the clinician determines the presence and nature of decelerations. There are four categories of decelerations. (i) Early deceleration is a decrease in the fetal heart beat 15 bpm under baseline for the peak of the contraction. Early decelerations return to baseline as the contraction ends. Early decelerations are benign, and usually indicate head compression. (ii) Variable deceleration, can be abrupt decreases in baseline up to 25 bpm below baseline, usually at the peak of a contraction. Variable decelerations return to baseline at the end of the contraction. Variable decelerations usually indicate umbilical cord compression. Variable decelerations require close monitoring, as they can be benign, or become indication of fetal distress. (ii) Late decelerations are defined as a gradual decrease in fetal heart beat of 1-15 bpm below baseline, which occur after the nadir of a uterine contraction, and return to baseline after the contraction is completed. Late decelerations usually indicate placental insufficiency, and indicate fetal distress. Delivery should be imminent when a repetitive pattern of late decelerations is noted, especially if variability is also minimal. (iii) Prolonged decelerations are defined as deceleration 1-25 bpm below baseline for 2 or more minutes. Prolonged decelerations are indicators of fetal distress, and fetal hypoxia may be suspected.
EFM also records uterine activity. Interpretation of uterine activity in EFM includes the frequency and duration of contractions. Frequency is determined by counting the minutes between the start of one contraction, to the start of the next contraction. Duration is the time (generally indicated in seconds) between the beginning and end of a contraction. For example, uterine contractions can be every 3 minutes, lasting 60 seconds. External monitoring cannot measure strength of contractions quantitatively. Absent a quantitative measure, clinicians judge the strength of contractions by palpating the fundus during a contraction, observing the patients response to the contraction, and considering the progression of cervical change.
Description of the Related Art Section Disclaimer: To the extent that specific patents/publications are discussed above in this Description of the Related Art Section or elsewhere in this Application, these discussions should not be taken as an admission that the discussed patents/publications are prior art for patent law purposes. For example, some or all of the discussed patents/publications may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific patents/publications are discussed above in this Description of the Related Art Section and/or throughout the application, they are all hereby incorporated by reference into this document in their respective entirety(ies).